In a manufacturing process of semiconductor devices, various heat treatment processes such as film forming, pattern etching, oxidation and diffusion, quality modification, annealing and the like are repeatedly performed. As a heat treating device for performing a specified heat treatment on a substrate such as a silicon wafer at a high temperature greater than or equal to 400° C. in a short period of time as possible, a rapid heating device (lamp annealing device) which rapidly heats the substrate by irradiating light from a light source thereto has been used (see, for example, Japanese Patent Laid-open Publication No. 2005-101237, Japanese Patent Laid-open Publication No. 2001-237195, Japanese Utility Model No. 3017978 and Japanese Patent Laid-open Publication No. H07-29843).
A heat treating device disclosed in Japanese Patent Laid-open Publication No. 2005-101237 includes a plurality of light sources attached to substantially an entire bottom surface of a ceiling portion of a lamp housing, which serves as a heating unit for rapidly heating a target object, e.g., a wafer. The bottom surface of the ceiling portion is a reflective surface formed of a planar surface or a cone surface, and a heat ray emitted from each light source is reflected towards the wafer located below. Further, the light sources located at the center portion of the lamp housing are disposed in such a manner that the radiation directions of the heat rays thereof point vertically downwards and the light sources located at the peripheral portion of the lamp housing are disposed so that the radiation direction of the heat rays thereof are tilted inwardly downwardly. In this way, the radiation directions of the heat rays are focused on the peripheral portion of the wafer.
A flash irradiation heating device disclosed in Japanese Patent Laid-open Publication No. 2001-237195 has a plurality of flash discharge lamps formed of straight pipes arranged in plural lines, which are installed above a work and in parallel with the work. Installed above the flash discharge lamp is a reflective mirror for reflecting flash from each flash discharge lamp downward. The reflective mirror is of a flat plate shape, and both end portions thereof are slightly bent downward at a predetermined angle.
In a beam heater disclosed in Japanese Utility Model No. 3017978, disposed in a lamp housing with a plurality of heat transfer holes in its peripheral portion is a reflective mirror of a hemispherical shape whose inner surface is a reflective surface. A halogen lamp is disposed inside the reflective mirror, and therefore, light emitted from the halogen lamp is reflected at the reflective surface and focused in a spot on a work disposed below.
In a heat treating device disclosed in Japanese Patent Laid-open Publication No. H07-29843, a plurality of light sources is disposed inside a lamp housing whose inner surface is a reflective surface of a dome shape (hemispherical shape), and light from the light sources is reflected downward by the reflective surface to be directed to a surface of a semiconductor wafer. As the light sources, a plurality of ring-shaped halogen lamps having different diameters or a plurality of bulb-type lamps as a point light source are used.
Meanwhile, if various heat treatment processes such as film forming, pattern etching, oxidation and diffusion, quality modification, annealing and the like are performed in the manufacturing process of the semiconductor devices, the surface of the substrate needs to be heated to a predetermined temperature in a short time. Further, the substrate is heated such that it has a uniform temperature distribution over the entire surface thereof.
However, the heat treating device disclosed in Japanese Patent Laid-open Publication No. 2005-101237 and the flash irradiation heating device disclosed in Japanese Patent Laid-open Publication No. 2001-237195 use a reflector whose reflective surface is of a planar surface or a cone surface. Therefore, it is difficult to collect light emitted from each light source in high density and direct the light to a predetermined position, and it is also difficult to uniformly heat the entire surface. In particular, it is extremely difficult to apply the devices to a substrate with a large diameter of, e.g., 300 mm.
To the contrary, the beam heater with a hemispheric reflective surface disclosed in Japanese Utility Model No. 3017978 and the heat treating device disclosed in Japanese Patent Laid-open Publication No. H07-29843 can have the uniform illumination distribution at the planar surface (bottom surface) of a hemispherical shape according to a solid angle projection theorem. Accordingly, the temperature can be uniformly distributed over the entire surface of the substrate. However, since the irradiation area becomes small if the substrate is disposed at the focal point of the reflector, the number of the light sources needs to be increased in order to irradiate the whole surface of the substrate. On the other hand, if the substrate is offset from the focal point, the larger area of the substrate can be irradiated, and therefore, the number of the light sources can be reduced. However, the intensity of the light is weak, resulting in decreased heating efficiency. Further, in the event that the intensity of the light emitted from the light source is increased by increasing an electric current flowing through the filament of the light source in order to enhance heating efficiency, the substrate can be rapidly heated, but there occurs a problem that the durability of the light source is reduced.
Therefore, various experiments have been performed with respect to the collection of the light. As a result, it has been found that the light emitted from the light source can be efficiently directed to the substrate by using a complex reflector including two types of reflectors and the substrate can be rapidly heated to a specific high temperature.